Speaker
Jeremiah P. Ostriker
(Princeton University)
Description
Massive elliptical galaxies universally host in their centers black holes with masses roughly proportional to the stellar masses of the hosts. Periodically, gas will accumulate at the centers of these systems due either (at early times) due to cosmological infall or (at later times) to secondary gas consequent to normal stellar evolution. This material will fuel central star-formation episodes and also AGN outbursts. I will describe work with Luca Ciotti, Ena Choi, Greg Novak and Thorsten Naab showing how the resultant AGN feedback influences the evolution of the elliptical galaxies. The two dominant processes are the interaction of the outflowing BAL wind with ambient gas in the galaxy and the X-ray induced heating and radiation pressure on the centrally located gas. Of real but lesser importance is UV radiation pressure on galactic dust. For all of these processes momentum driving is the principal actor with “thermal” feedback relatively unimportant. AGN feedback keeps the central gas in elliptical galaxies at a low level and results in the observed very small duty cycle (10-2 - 10-3) of AGN flaring. It also regulates the heating of the ambient gaseous halos of ellipticals, maintaining them in the observed range of X-ray luminosity. Finally, recent cosmological simulations show that winds from AGN are extremely effective in maintaining ellipticals at late times in the “red and dead”, “quenched” state.
Author
Jeremiah P. Ostriker
(Princeton University)